Consumer demands have fueled technological advances in the area of electronics. Through aggressive development and manufacturing, the industry has accomplished increased miniaturization of electronic components resulting in the advent of extremely lightweight and dimensionally constrained hand held portable electronic devices. Such devices, including portable radiotelephones, are typically battery powered. The operational longevity of the radiotelephone based on its associated battery life often becomes a fundamental consumer selling point. In order to maximize battery use and, thus, satisfy consumer demands, the radiotelephone must be developed to optimize power consumption.
Essential to the operation of the radiotelephone, as well as to other two-way communication devices, is an amplifier. An amplifier is utilized to amplify radio frequency (RF) signals for transmission so as to permit the radiotelephone to communicate with a fixed site transceiver, which, in turn, is interfaced between the landline telephone system and other multiple, portable, or mobile radiotelephone systems contained within a geographic area. Existing amplifiers typically utilize amplifying elements comprised of a FET (Field Effect Transistor). Recently, the industry has shifted away from utilizing a silicon MOSFET (metal oxide semiconductor FET) and toward utilizing a gallium arsenide FET for increased efficiency. The gallium arsenide FET is biased into operation via the application of a negative voltage to the gate thereof.
To facilitate design and manufacturability of radiotelephones utilizing gallium arsenide FETs, the gate voltage required to bias the gallium arsenide FET into operation is typically set to a constant negative voltage. The amplifier of the radiotelephone may utilize as much as 500 mA of current to amplify RF signals to output power levels on the magnitude of 29 dBm. Thus, the amplifier must be operated as efficiently as possible so as to make battery-powered handheld radiotelephones feasible.
Therefore, what is needed is a method and apparatus for increasing the efficiency of amplifiers, especially those amplifiers utilizing gallium arsenide FET amplifying elements.